This study investigated the impact of a cylindrical obstacle on convection in an inclined square cavity filled with water-Al2O3 nanofluid. Using the finite volume method, the problem was resolved by having the inner cylinder rotate adiabatically while other walls were thermally insulated. Additionally, the bottom wall was hotter than the top. The study examined the effects of cylindrical obstacle radius (0.1 ≤ R ≤ 0.2), rotation speed (-500 ≤ Ω ≤ 500), Richardson number (0.01 ≤ Ri ≤ 100), volumetric nanoparticle fraction (0.02), and Grashof number (Gr=104) on heat transfer rate or Nusselt number. The results were compared with previous literature, and the influence of the cylindrical obstacle rotational speed on convection flow was evaluated. An increase in the counterclockwise angular rotating speed resulted in higher nanofluid flux. The heat transmission coefficient increased as the Richardson number decreased. The use of nanofluid in the enclosure increased the coefficient of heat flow through mixed convection. Finally, the study showed that the convection heat exchange is enhanced with the increase in the radius. Moreover, an enhancement of the Nusselt number around 46% was reported for the cylinder, under Gr=10000, ∅=0.02, γ=45° and Ri=10.